Which test is most diagnostic for confirming iron deficiency anemia?

Serum ferritin levels are the most diagnostic test for confirming iron deficiency anemia because ferritin is a protein that stores iron in the body. A low serum ferritin level indicates that the body has insufficient iron stores, which is a hallmark of iron deficiency anemia. This test provides direct evidence of iron deficiency by measuring the available iron in storage, making it a reliable indicator for diagnosing this condition.

In contrast, while a complete blood count can show signs of anemia (such as low hemoglobin and hematocrit levels), it does not specifically diagnose the underlying cause of the anemia. A bone marrow biopsy, although it can provide detailed information about the bone marrow's condition and iron stores, is an invasive procedure and is typically reserved for more complex cases that require further investigation. The reticulocyte count assesses the production of new red blood cells but does not specifically measure iron levels or diagnose iron deficiency directly. Therefore, serum ferritin is the most effective test for confirming iron deficiency anemia.